Closed caption tagging system

ABSTRACT

A closed caption tagging system provides a mechanism for inserting tags into an audio or video television broadcast stream prior to or at the time of transmission. The tags contain command and control information that the receiver translates and acts upon. The receiver receives the broadcast stream and detects and processes the tags within the broadcast stream which is stored on a storage device that resides on the receiver. Program material from the broadcast stream is played back to the viewer from the storage device. Tags indicate the start and end points of a program segment. Program segments such as commercials are automatically replaced by the receiver with new program segments that are selected based on various criteria.

CROSS-REFERENCE TO RELATED APPLICATIONS; PRIORITY CLAIM

This application claims benefit as a Divisional of application Ser. No.09/665,921 filed Sep. 20, 2000, which claims benefit of ProvisionalApplication 60/154,713, filed Sep. 20, 1999, and which is also aContinuation-In-Part of application Ser. No. 09/126,071 filed Jul. 30,1998, issued as U.S. Pat. No. 6,233,389 B1, on May 15, 2001, the entirecontents of which is hereby incorporated by reference as if fully setforth herein, under 35 U.S.C. §120.

TECHNICAL FIELD

The invention relates to the processing of multimedia audio and videostreams. More particularly, the invention relates to the tagging ofmultimedia audio and video television streams.

BACKGROUND

The Video Cassette Recorder (VCR) has changed the lives of television(TV) viewers throughout the world. The VCR has offered viewers theflexibility to time-shift TV programs to match their lifestyles.

The viewer stores TV programs onto magnetic tape using the VCR. The VCRgives the viewer the ability to play, rewind, fast forward and pause thestored program material. These functions enable the viewer to pause theprogram playback whenever he desires, fast forward through unwantedprogram material or commercials, and to replay favorite scenes. However,a VCR cannot both capture and play back information at the same time.

Digital Video Recorders (DVR) have recently entered into themarketplace. DVRs allow the viewer to store TV programs on a hard disk.This has freed the viewer from the magnetic tape realm. Viewers canpause, rewind, and fast forward live broadcast programs. However, thefunctionality of DVRs extends beyond recording programs.

Having programs stored locally in a digital form gives the programmermany more options than were previously available. Advertisements(commercials) can now be dynamically replaced and specifically targetedto the particular viewer based on his or her viewing habits. Thecommercials can be stored locally on the viewer's DVR and shown at anytime.

DVRs allow interactive programming with the viewer. Generally,promotions for future shows are displayed to viewers during the normalbroadcast programs. Viewers must then remember the date, time, andchannel that the program will be aired on to record or view the program.DVRs allow the viewer to schedule the recording of the programimmediately.

The only drawback is that the current generation of DVRs do not have thecapability to interact with the viewer at this level. There is no meansby which to notify the DVR that commercials are directly tied to acertain program or other advertisements. Further, there is no way totell the DVR that a commercial can be replaced.

It would be advantageous to provide a closed caption tagging system thatgives the content provider the ability to send frame specific dataacross broadcast media. It would further be advantageous to provide aclosed caption tagging system that allows the receiver to dynamicallyinteract with the viewer and configure itself based on program content.

SUMMARY

The invention provides a closed caption tagging system. The inventionallows content providers to send frame specific data and commandsintegrated into video and audio television streams across broadcastmedia. In addition, the invention allows the receiver to dynamicallyinteract with the viewer and configure itself based on video and audiostream content.

A preferred embodiment of the invention provides a mechanism forinserting tags into an audio or video television broadcast stream. Tagsare inserted into the broadcast stream prior to or at the time oftransmission. The tags contain command and control information that thereceiver translates and acts upon.

The receiver receives the broadcast stream and detects and processes thetags within the broadcast stream. The broadcast stream is stored on astorage device that resides on the receiver. Program material from thebroadcast stream is played back to the viewer from the storage device.

During the tag processing stage, the receiver performs the appropriateactions in response to the tags. The tags offer a great amount offlexibility to the content provider or system administrator to create alimitless amount of operations.

Tags indicate the start and end points of a program segment. Thereceiver skips over a program segment during playback in response to theviewer pressing a button on a remote input device. The receiver alsoautomatically skips over program segments depending on the viewer'spreferences.

Program segments such as commercials are automatically replaced by thereceiver with new program segments. New program segments are selectedbased on various criteria such as the locale, time of day, programmaterial, viewer's viewing habits, viewer's program preferences, or theviewer's personal information. The new program segments are storedremotely or locally on the receiver.

Menus, icons, and Web pages are displayed to the viewer based oninformation included in a tag. The viewer interacts with the menu, icon,or Web page through an input device. The receiver performs the actionsassociated with the menu, icon, or Web page and the viewer's input. If amenu or action requires that the viewer exit from the playback of theprogram material, then the receiver saves the exit point and returns theviewer back to the same exit point when the viewer has completed theinteraction session.

Menus and icons are used to generate leads, generate sales, and schedulethe recording of programs. A one-touch recording option is provided. Anicon is displayed to the viewer telling the viewer that an advertisedprogram is available for recording at a future time. The viewer pressesa single button on an input device causing the receiver to schedule theprogram for recording. The receiver will also record the current programin the broadcast stream onto the storage device based on informationincluded in a tag.

Tags are used to create indexes in program material. This allows theviewer to jump to particular indexes in a program.

Other aspects and advantages of the invention will become apparent fromthe following detailed description in combination with the accompanyingdrawings, illustrating, by way of example, the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block schematic diagram of a high level view of a preferredembodiment of the invention according to the invention;

FIG. 2 is a block schematic diagram of a preferred embodiment of theinvention using multiple input and output modules according to theinvention;

FIG. 3 is a schematic diagram of an Moving Pictures Experts Group (MPEG)data stream and its video and audio components according to theinvention;

FIG. 4 is a block schematic diagram of a parser and four direct memoryaccess (DMA) input engines contained in the Media Switch according tothe invention;

FIG. 5 is a schematic diagram of the components of a packetizedelementary stream (PES) buffer according to the invention;

FIG. 6 is a schematic diagram of the construction of a PES buffer fromthe parsed components in the Media Switch output circular buffers;

FIG. 7 is a block schematic diagram of the Media Switch and the variouscomponents that it communicates with according to the invention;

FIG. 8 is a block schematic diagram of a high level view of the programlogic according to the invention;

FIG. 9 is a block schematic diagram of a class hierarchy of the programlogic according to the invention;

FIG. 10 is a block schematic diagram of a preferred embodiment of theclip cache component of the invention according to the invention;

FIG. 11 is a block schematic diagram of a preferred embodiment of theinvention that emulates a broadcast studio video mixer according to theinvention;

FIG. 12 is a block schematic diagram of a closed caption parseraccording to the invention;

FIG. 13 is a block schematic diagram of a high level view of a preferredembodiment of the invention utilizing a VCR as an integral component ofthe invention according to the invention;

FIG. 14 is a block schematic diagram of a preferred embodiment of theinvention for inserting tags into a video stream according to theinvention;

FIG. 15 is a block schematic diagram of a server-based preferredembodiment of the invention for inserting tags into a video streamaccording to the invention;

FIG. 16 is a diagram of a user interface for inserting tags into a videostream according to the invention;

FIG. 17 is a diagram of a screen with an alert icon displayed in thelower left comer of the screen according to the invention;

FIG. 18 is a block schematic diagram of the transmission route of avideo stream according to the invention;

FIG. 19 is a block schematic diagram of the tagging of the start and endof a program segment of a video stream and the playback of a new programsegment according to the invention;

FIG. 20 is a block schematic diagram of a preferred embodiment of theinvention that interprets tags inserted into a video stream according tothe invention;

FIG. 21 is a diagram of a screen displaying program recording optionsaccording to the invention;

FIG. 22 is a diagram of a viewer remote control device according to theinvention; and

FIG. 23 is a block schematic diagram of a series of screens for lead andsale generation according to the invention.

DETAILED DESCRIPTION

The invention is embodied in a closed caption tagging system. A systemaccording to the invention allows content providers to send framespecific data and commands integrated into video and audio televisionstreams across broadcast media. The invention additionally allows thereceiver to dynamically interact with the viewer and configure itselfbased on video and audio stream content.

A preferred embodiment of the invention provides a tagging andinterpretation system that allows a content provider to tag, in a framespecific manner, video and audio streams transmitted over televisionbroadcast media. A receiver interprets and acts upon the tags embeddedin the received stream. The tag data allow the receiver to dynamicallyinteract with the viewer through menus and action icons. The tags alsoprovide for the dynamic configuration of the receiver.

Referring to FIG. 1, a preferred embodiment of the invention has anInput Section 101, Media Switch 102, and an Output Section 103. TheInput Section 101 takes television (TV) input streams in a multitude offorms, for example, National Television Standards Committee (NTSC) orPAL broadcast, and digital forms such as Digital Satellite System (DSS),Digital Broadcast Services (DBS), or Advanced Television StandardsCommittee (ATSC). DBS, DSS and ATSC are based on standards called MovingPictures Experts Group 2 (MPEG2) and MPEG2 Transport. MPEG2 Transport isa standard for formatting the digital data stream from the TV sourcetransmitter so that a TV receiver can disassemble the input stream tofind programs in the multiplexed signal. The Input Section 101 producesMPEG streams. An MPEG2 transport multiplex supports multiple programs inthe same broadcast channel, with multiple video and audio feeds andprivate data. The Input Section 101 tunes the channel to a particularprogram, extracts a specific MPEG program out of it, and feeds it to therest of the system. Analog TV signals are encoded into a similar MPEGformat using separate video and audio encoders, such that the remainderof the system is unaware of how the signal was obtained. Information maybe modulated into the Vertical Blanking Interval (VBI) of the analog TVsignal in a number of standard ways; for example, the North AmericanBroadcast Teletext Standard (NABTS) may be used to modulate informationonto lines 10 through 20 of an NTSC signal, while the FCC mandates theuse of line 21 for Closed Caption (CC) and Extended Data Services (EDS).Such signals are decoded by the input section and passed to the othersections as if they were delivered via an MPEG2 private data channel.

The Media Switch 102 mediates between a microprocessor CPU 106, harddisk or storage device 105, and memory 104. Input streams are convertedto an MPEG stream and sent to the Media Switch 102. The Media Switch 102buffers the MPEG stream into memory. It then performs two operations ifthe user is watching real time TV: the stream is sent to the OutputSection 103 and it is written simultaneously to the hard disk or storagedevice 105.

The Output Section 103 takes MPEG streams as input and produces ananalog TV signal according to the NTSC, PAL, or other required TVstandards. The Output Section 103 contains an MPEG decoder, On-ScreenDisplay (OSD) generator, analog TV encoder and audio logic. The OSDgenerator allows the program logic to supply images which will beoverlayed on top of the resulting analog TV signal. Additionally, theOutput Section can modulate information supplied by the program logiconto the VBI of the output signal in a number of standard formats,including NABTS, CC and EDS.

With respect to FIG. 2, the invention easily expands to accommodatemultiple Input Sections (tuners) 201, 202, 203, 204, each can be tunedto different types of input. Multiple Output Modules (decoders) 206,207, 208, 209 are added as well. Special effects such as picture in apicture can be implemented with multiple decoders. The Media Switch 205records one program while the user is watching another. This means thata stream can be extracted off the disk while another stream is beingstored onto the disk.

Referring to FIG. 3, the incoming MPEG stream 301 has interleaved video302, 305, 306 and audio 303, 304, 307 segments. These elements must beseparated and recombined to create separate video 308 and audio 309streams or buffers. This is necessary because separate decoders are usedto convert MPEG elements back into audio or video analog components.Such separate delivery requires that time sequence information begenerated so that the decoders may be properly synchronized for accurateplayback of the signal.

The Media Switch enables the program logic to associate proper timesequence information with each segment, possibly embedding it directlyinto the stream. The time sequence information for each segment iscalled a time stamp. These time stamps are monotonically increasing andstart at zero each time the system boots up. This allows the inventionto find any particular spot in any particular video segment. Forexample, if the system needs to read five seconds into an incomingcontiguous video stream that is being cached, the system simply has tostart reading forward into the stream and look for the appropriate timestamp.

A binary search can be performed on a stored file to index into astream. Each stream is stored as a sequence of fixed-size segmentsenabling fast binary searches because of the uniform timestamping. Ifthe user wants to start in the middle of the program, the systemperforms a binary search of the stored segments until it finds theappropriate spot, obtaining the desired results with a minimal amount ofinformation. If the signal were instead stored as an MPEG stream, itwould be necessary to linearly parse the stream from the beginning tofind the desired location.

With respect to FIG. 4, the Media Switch contains four input DirectMemory Access (DMA) engines 402, 403, 404, 405 each DMA engine has anassociated buffer 410, 411, 412, 413. Conceptually, each DMA engine hasa pointer 406, a limit for that pointer 407, a next pointer 408, and alimit for the next pointer 409. Each DMA engine is dedicated to aparticular type of information, for example, video 402, audio 403, andparsed events 405. The buffers 410, 411, 412, 413 are circular andcollect the specific information. The DMA engine increments the pointer406 into the associated buffer until it reaches the limit 407 and thenloads the next pointer 408 and limit 409. Setting the pointer 406 andnext pointer 408 to the same value, along with the corresponding limitvalue creates a circular buffer. The next pointer 408 can be set to adifferent address to provide vector DMA.

The input stream flows through a parser 401. The parser 401 parses thestream looking for MPEG distinguished events indicating the start ofvideo, audio or private data segments. For example, when the parser 401finds a video event, it directs the stream to the video DMA engine 402.The parser 401 buffers up data and DMAs it into the video buffer 410through the video DMA engine 402. At the same time, the parser 401directs an event to the event DMA engine 405 which generates an eventinto the event buffer 413. When the parser 401 sees an audio event, itredirects the byte stream to the audio DMA engine 403 and generates anevent into the event buffer 413. Similarly, when the parser 401 sees aprivate data event, it directs the byte stream to the private data DMAengine 404 and directs an event to the event buffer 413. The MediaSwitch notifies the program logic via an interrupt mechanism when eventsare placed in the event buffer.

Referring to FIGS. 4 and 5, the event buffer 413 is filled by the parser401 with events. Each event 501 in the event buffer has an offset 502,event type 503, and time stamp field 504. The parser 401 provides thetype and offset of each event as it is placed into the buffer. Forexample, when an audio event occurs, the event type field is set to anaudio event and the offset indicates the location in the audio buffer411. The program logic knows where the audio buffer 411 starts and addsthe offset to find the event in the stream. The address offset 502 tellsthe program logic where the next event occurred, but not where it ended.The previous event is cached so the end of the current event can befound as well as the length of the segment.

With respect to FIGS. 5 and 6, the program logic reads accumulatedevents in the event buffer 602 when it is interrupted by the MediaSwitch 601. From these events the program logic generates a sequence oflogical segments 603 which correspond to the parsed MPEG segments 615.The program logic converts the offset 502 into the actual address 610 ofeach segment, and records the event length 609 using the last cachedevent. If the stream was produced by encoding an analog signal, it willnot contain Program Time Stamp (PTS) values, which are used by thedecoders to properly present the resulting output. Thus, the programlogic uses the generated time stamp 504 to calculate a simulated PTS foreach segment and places that into the logical segment timestamp 607. Inthe case of a digital TV stream, PTS values are already encoded in thestream. The program logic extracts this information and places it in thelogical segment timestamp 607.

The program logic continues collecting logical segments 603 until itreaches the fixed buffer size. When this occurs, the program logicgenerates a new buffer, called a Packetized Elementary Stream (PES) 605buffer containing these logical segments 603 in order, plus ancillarycontrol information. Each logical segment points 604 directly to thecircular buffer,e.g., the video buffer 613, filled by the Media Switch601. This new buffer is then passed to other logic components, which mayfurther process the stream in the buffer in some way, such as presentingit for decoding or writing it to the storage media. Thus, the MPEG datais not copied from one location in memory to another by the processor.This results in a more cost effective design since lower memorybandwidth and processor bandwidth is required.

A unique feature of the MPEG stream transformation into PES buffers isthat the data associated with logical segments need not be present inthe buffer itself, as presented above. When a PES buffer is written tostorage, these logical segments are written to the storage medium in thelogical order in which they appear. This has the effect of gatheringcomponents of the stream, whether they be in the video, audio or privatedata circular buffers, into a single linear buffer of stream data on thestorage medium. The buffer is read back from the storage medium with asingle transfer from the storage media, and the logical segmentinformation is updated to correspond with the actual locations in thebuffer 606. Higher level program logic is unaware of thistransformation, since it handles only the logical segments, thus streamdata is easily managed without requiring that the data ever be copiedbetween locations in DRAM by the CPU.

A unique aspect of the Media Switch is the ability to handle high datarates effectively and inexpensively. It performs the functions of takingvideo and audio data in, sending video and audio data out, sending videoand audio data to disk, and extracting video and audio data from thedisk on a low cost platform. Generally, the Media Switch runsasynchronously and autonomously with the microprocessor CPU, using itsDMA capabilities to move large quantities of information with minimalintervention by the CPU.

Referring to FIG. 7, the input side of the Media Switch 701 is connectedto an MPEG encoder 703. There are also circuits specific to MPEG audio704 and vertical blanking interval (VBI) data 702 feeding into the MediaSwitch 701. If a digital TV signal is being processed instead, the MPEGencoder 703 is replaced with an MPEG2 Transport Demultiplexor, and theMPEG audio encoder 704 and VBI decoder 702 are deleted. Thedemultiplexor multiplexes the extracted audio, video and private datachannel streams through the video input Media Switch port.

The parser 705 parses the input data stream from the MPEG encoder 703,audio encoder 704 and VBI decoder 702, or from the transportdemultiplexor in the case of a digital TV stream. The parser 705 detectsthe beginning of all of the important events in a video or audio stream,the start of all of the frames, the start of sequence headers—all of thepieces of information that the program logic needs to know about inorder to both properly play back and perform special effects on thestream, e.g. fast forward, reverse, play, pause, fast/slow play,indexing, and fast/slow reverse play.

The parser 705 places tags 707 into the FIFO 706 when it identifiesvideo or audio segments, or is given private data. The DMA 709 controlswhen these tags are taken out. The tags 707 and the DMA addresses of thesegments are placed into the event queue 708. The frame typeinformation, whether it is a start of a video I-frame, video B-frame,video P-frame, video PES, audio PES, a sequence header, an audio frame,or private data packet, is placed into the event queue 708 along withthe offset in the related circular buffer where the piece of informationwas placed. The program logic operating in the CPU 713 examines eventsin the circular buffer after it is transferred to the DRAM 714.

The Media Switch 701 has a data bus 711 that connects to the CPU 713 andDRAM 714. An address bus 712 is also shared between the Media Switch701, CPU 713, and DRAM 714. A hard disk or storage device 710 isconnected to one of the ports of the Media Switch 701. The Media Switch701 outputs streams to an MPEG video decoder 715 and a separate audiodecoder 717. The audio decoder 717 signals contain audio cues generatedby the system in response to the user's commands on a remote control orother internal events. The decoded audio output from the MPEG decoder isdigitally mixed 718 with the separate audio signal. The resultingsignals contain video, audio, and on-screen displays and are sent to theTV 716.

The Media Switch 701 takes in 8-bit data and sends it to the disk, whileat the same time extracts another stream of data off of the disk andsends it to the MPEG decoder 715. All of the DMA engines described abovecan be working at the same time. The Media Switch 701 can be implementedin hardware using a Field Programmable Gate Array (FPGA), ASIC, ordiscrete logic.

Rather than having to parse through an immense data stream looking forthe start of where each frame would be, the program logic only has tolook at the circular event buffer in DRAM 714 and it can tell where thestart of each frame is and the frame type. This approach saves a largeamount of CPU power, keeping the real time requirements of the CPU 713small. The CPU 713 does not have to be very fast at any point in time.The Media Switch 701 gives the CPU 713 as much time as possible tocomplete tasks. The parsing mechanism 705 and event queue 708 decouplethe CPU 713 from parsing the audio, video, and buffers and the real timenature of the streams, which allows for lower costs. It also allows theuse of a bus structure in a CPU environment that operates at a muchlower clock rate with much cheaper memory than would be requiredotherwise.

The CPU 713 has the ability to queue up one DMA transfer and can set upthe next DMA transfer at its leisure. This gives the CPU 713 large timeintervals within which it can service the DMA controller 709. The CPU713 may respond to a DMA interrupt within a larger time window becauseof the large latency allowed. MPEG streams, whether extracted from anMPEG2 Transport or encoded from an analog TV signal, are typicallyencoded using a technique called Variable Bit Rate encoding (VBR). Thistechnique varies the amount of data required to represent a sequence ofimages by the amount of movement between those images. This techniquecan greatly reduce the required bandwidth for a signal, howeversequences with rapid movement (such as a basketball game) may be encodedwith much greater bandwidth requirements. For example, the HughesDirecTV satellite system encodes signals with anywhere from 1 to 10 Mb/sof required bandwidth, varying from frame to frame. It would bedifficult for any computer system to keep up with such rapidly varyingdata rates without this structure.

With respect to FIG. 8, the program logic within the CPU has threeconceptual components: sources 801, transforms 802, and sinks 803. Thesources 801 produce buffers of data. Transforms 802 process buffers ofdata and sinks 803 consume buffers of data. A transform is responsiblefor allocating and queuing the buffers of data on which it will operate.Buffers are allocated as if “empty” to sources of data, which give themback “full”. The buffers are then queued and given to sinks as “full”,and the sink will return the buffer “empty”.

A source 801 accepts data from encoders, e.g., a digital satellitereceiver. It acquires buffers for this data from the downstreamtransform, packages the data into a buffer, then pushes the buffer downthe pipeline as described above. The source object 801 does not knowanything about the rest of the system. The sink 803 consumes buffers,taking a buffer from the upstream transform, sending the data to thedecoder, and then releasing the buffer for reuse.

There are two types of transforms 802 used: spatial and temporal.Spatial transforms are transforms that perform, for example, an imageconvolution or compression/decompression on the buffered data that ispassing through. Temporal transforms are used when there is no timerelation that is expressible between buffers going in and buffers comingout of a system. Such a transform writes the buffer to a file 804 on thestorage medium. The buffer is pulled out at a later time, sent down thepipeline, and properly sequenced within the stream.

Referring to FIG. 9, a C++ class hierarchy derivation of the programlogic is shown. The TiVo Media Kernel (Tmk) 904, 908, 913 mediates withthe operating system kernel. The kernel provides operations such as:memory allocation, synchronization, and threading. The TmkCore 904, 908,913 structures memory taken from the media kernel as an object. Itprovides operators, new and delete, for constructing and deconstructingthe object. Each object (source 901, transform 902, and sink 903) ismulti-threaded by definition and can run in parallel.

The TmkPipeline class 905, 909, 914 is responsible for flow controlthrough the system. The pipelines point to the next pipeline in the flowfrom source 901 to sink 903. To pause the pipeline, for example, anevent called “pause” is sent to the first object in the pipeline. Theevent is relayed on to the next object and so on down the pipeline. Thisall happens asynchronously to the data going through the pipeline. Thus,similar to applications such as telephony, control of the flow of MPEGstreams is asynchronous and separate from the streams themselves. Thisallows for a simple logic design that is at the same time powerfulenough to support the features described previously, including pause,rewind, fast forward and others. In addition, this structure allows fastand efficient switching between stream sources, since buffered data canbe simply discarded and decoders reset using a single event, after whichdata from the new stream will pass down the pipeline. Such a capabilityis needed, for example, when switching the channel being captured by theinput section, or when switching between a live signal from the inputsection and a stored stream.

The source object 901 is a TmkSource 906 and the transform object 902 isa TmkXfrm 910. These are intermediate classes that define standardbehaviors for the classes in the pipeline. Conceptually, they handshakebuffers down the pipeline. The source object 901 takes data out of aphysical data source, such as the Media Switch, and places it into a PESbuffer. To obtain the buffer, the source object 901 asks the down streamobject in his pipeline for a buffer (allocEmptyBuf). The source object901 is blocked until there is sufficient memory. This means that thepipeline is self-regulating; it has automatic flow control. When thesource object 901 has filled up the buffer, it hands it back to thetransform 902 through the pushFullBuf function.

The sink 903 is flow controlled as well. It calls nextFullBuf whichtells the transform 902 that it is ready for the next filled buffer.This operation can block the sink 903 until a buffer is ready. When thesink 903 is finished with a buffer (i. e., it has consumed the data inthe buffer) it calls releaseEmptyBuf. ReleaseEmptyBuf gives the bufferback to the transform 902. The transform 902 can then hand that buffer,for example, back to the source object 901 to fill up again. In additionto the automatic flow-control benefit of this method, it also providesfor limiting the amount of memory dedicated to buffers by allowingenforcement of a fixed allocation of buffers by a transform. This is animportant feature in achieving a cost-effective limited DRAMenvironment.

The MediaSwitch class 909 calls the allocEmptyBuf method of theTmkClipCache 912 object and receives a PES buffer from it. It then goesout to the circular buffers in the Media Switch hardware and generatesPES buffers. The MediaSwitch class 909 fills the buffer up and pushes itback to the TmkClipCache 912 object.

The TmkClipCache 912 maintains a cache file 918 on a storage medium. Italso maintains two pointers into this cache: a push pointer 919 thatshows where the next buffer coming from the source 901 is inserted; anda current pointer 920 which points to the current buffer used.

The buffer that is pointed to by the current pointer is handed to theVela decoder class 916. The Vela decoder class 916 talks to the decoder921 in the hardware. The decoder 921 produces a decoded TV signal thatis subsequently encoded into an analog TV signal in NTSC, PAL or otheranalog format. When the Vela decoder class 916 is finished with thebuffer it calls releaseEmptyBuf.

The structure of the classes makes the system easy to test and debug.Each level can be tested separately to make sure it performs in theappropriate manner, and the classes may be gradually aggregated toachieve the desired functionality while retaining the ability toeffectively test each object.

The control object 917 accepts commands from the user and sends eventsinto the pipeline to control what the pipeline is doing. For example, ifthe user has a remote control and is watching TV, the user presses pauseand the control object 917 sends an event to the sink 903, that tells itpause. The sink 903 stops asking for new buffers. The current pointer920 stays where it is at. The sink 903 starts taking buffers out againwhen it receives another event that tells it to play. The system is inperfect synchronization; it starts from the frame that it stopped at.

The remote control may also have a fast forward key. When the fastforward key is pressed, the control object 917 sends an event to thetransform 902, that tells it to move forward two seconds. The transform902 finds that the two second time span requires it to move forwardthree buffers. It then issues a reset event to the downstream pipeline,so that any queued data or state that may be present in the hardwaredecoders is flushed. This is a critical step, since the structure ofMPEG streams requires maintenance of state across multiple frames ofdata, and that state will be rendered invalid by repositioning thepointer. It then moves the current pointer 920 forward three buffers.The next time the sink 903 calls nextFullBuf it gets the new currentbuffer. The same method works for fast reverse in that the transform 902moves the current pointer 920 backwards.

A system clock reference resides in the decoder. The system clockreference is sped up for fast play or slowed down for slow play. Thesink simply asks for full buffers faster or slower, depending on theclock speed.

With respect to FIG. 10, two other objects derived from the TmkXfrmclass are placed in the pipeline for disk access. One is calledTmkClipReader 1003 and the other is called TmkClipWriter 1001. Bufferscome into the TmkClipWriter 1001 and are pushed to a file on a storagemedium 1004. TmkClipReader 1003 asks for buffers which are taken off ofa file on a storage medium 1005. A TmkClipReader 1003 provides only theallocEmptyBuf and pushFullBuf methods, while a TmkClipWriter 1001provides only the nextFullBuf and releaseEmptyBuf methods. ATmkClipReader 1003 therefore performs the same function as the input, or“push” side of a TmkClipCache 1002, while a TmkClipWriter 1001 thereforeperforms the same function as the output, or “pull” side of aTmkClipCache 1002.

Referring to FIG. 11, a preferred embodiment that accomplishes multiplefunctions is shown. A source 1101 has a TV signal input. The sourcesends data to a PushSwitch 1102 which is a transform derived fromTmkXfrm. The PushSwitch 1102 has multiple outputs that can be switchedby the control object 1114. This means that one part of the pipeline canbe stopped and another can be started at the users whim. The user canswitch to different storage devices. The PushSwitch 1102 could output toa TmkClipWriter 1106, which goes onto a storage device 1107 or write tothe cache transform 1103.

An important feature of this apparatus is the ease with which it canselectively capture portions of an incoming signal under the control ofprogram logic. Based on information such as the current time, or perhapsa specific time span, or perhaps via a remote control button press bythe viewer, a TmkClipWriter 1106 may be switched on to record a portionof the signal, and switched off at some later time. This switching istypically caused by sending a “switch” event to the PushSwitch 1102object.

An additional method for triggering selective capture is throughinformation modulated into the VBI or placed into an MPEG private datachannel. Data decoded from the VBI or private data channel is passed tothe program logic. The program logic examines this data to determine ifthe data indicates that capture of the TV signal into which it wasmodulated should begin. Similarly, this information may also indicatewhen recording should end, or another data item may be modulated intothe signal indicating when the capture should end. The starting andending indicators may be explicitly modulated into the signal or otherinformation that is placed into the signal in a standard fashion may beused to encode this information.

With respect to FIG. 12, an example is shown which demonstrates how theprogram logic scans the words contained within the closed caption (CC)fields to determine starting and ending times, using particular words orphrases to trigger the capture. A stream of NTSC or PAL fields 1201 ispresented. CC bytes are extracted from each odd field 1202, and enteredin a circular buffer 1203 for processing by the Word Parser 1204. TheWord Parser 1204 collects characters until it encounters a wordboundary, usually a space, period or other delineating character. Recallfrom above, that the MPEG audio and video segments are collected into aseries of fixed-size PES buffers. A special segment is added to each PESbuffer to hold the words extracted from the CC field 1205. Thus, the CCinformation is preserved in time synchronization with the audio andvideo, and can be correctly presented to the viewer when the stream isdisplayed. This also allows the stored stream to be processed for CCinformation at the leisure of the program logic, which spreads out load,reducing cost and improving efficiency. In such a case, the words storedin the special segment are simply passed to the state table logic 1206.

During stream capture, each word is looked up in a table 1206 whichindicates the action to take on recognizing that word. This action maysimply change the state of the recognizer state machine 1207, or maycause the state machine 1207 to issue an action request, such as “startcapture”, “stop capture”, “phrase seen”, or other similar requests.Indeed, a recognized word or phrase may cause the pipeline to beswitched; for example, to overlay a different audio track if undesirablelanguage is used in the program.

Note that the parsing state table 1206 and recognizer state machine 1207may be modified or changed at any time. For example, a different tableand state machine may be provided for each input channel. Alternatively,these elements may be switched depending on the time of day, or becauseof other events.

Referring to FIG. 11, a PullSwitch is added 1104 which outputs to thesink 1105. The sink 1105 calls nextFullBuf and releaseEmptyBuf to get orreturn buffers from the PullSwitch 1104. The PullSwitch 1104 can haveany number of inputs. One input could be an ActionClip 1113. The remotecontrol can switch between input sources. The control object 1114 sendsan event to the PullSwitch 1104, telling it to switch. It will switchfrom the current input source to whatever input source the controlobject selects.

An ActionClip class provides for sequencing a number of different storedsignals in a predictable and controllable manner, possibly with theadded control of viewer selection via a remote control. Thus, it appearsas a derivative of a TmkXfrm object that accepts a “switch” event forswitching to the next stored signal.

This allows the program logic or user to create custom sequences ofvideo output. Any number of video segments can be lined up and combinedas if the program logic or user were using a broadcast studio videomixer. TmkClipReaders 1108, 1109, 1110 are allocated and each is hookedinto the PullSwitch 1104. The PullSwitch 1104 switches between theTmkClipReaders 1108, 1109, 1110 to combine video and audio clips. Flowcontrol is automatic because of the way the pipeline is constructed. ThePush and Pull Switches are the same as video switches in a broadcaststudio.

The derived class and resulting objects described here may be combinedin an arbitrary way to create a number of different usefulconfigurations for storing, retrieving, switching and viewing of TVstreams. For example, if multiple input and output sections areavailable, one input is viewed while another is stored, and apicture-in-picture window generated by the second output is used topreview previously stored streams. Such configurations represent aunique and novel application of software transformations to achieve thefunctionality expected of expensive, sophisticated hardware solutionswithin a single cost-effective device.

With respect to FIG. 13, a high-level system view is shown whichimplements a VCR backup. The Output Module 1303 sends TV signals to theVCR 1307. This allows the user to record TV programs directly on tovideo tape. The invention allows the user to queue up programs from diskto be recorded on to video tape and to schedule the time that theprograms are sent to the VCR 1307. Title pages (EPG data) can be sent tothe VCR 1307 before a program is sent. Longer programs can be scaled tofit onto smaller video tapes by speeding up the play speed or droppingframes.

The VCR 1307 output can also be routed back into the Input Module 1301.In this configuration the VCR acts as a backup system for the MediaSwitch 1302. Any overflow storage or lower priority programming is sentto the VCR 1307 for later retrieval.

The Input Module 1301 can decode and pass to the remainder of the systeminformation encoded on the Vertical Blanking Interval (VBI). The OutputModule 1303 can encode into the output VBI data provided by theremainder of the system. The program logic may arrange to encodeidentifying information of various kinds into the output signal, whichwill be recorded onto tape using the VCR 1307. Playing this tape backinto the input allows the program logic to read back this identifyinginformation, such that the TV signal recorded on the tape is properlyhandled. For example, a particular program may be recorded to tape alongwith information about when it was recorded, the source network, etc.When this program is played back into the Input Module, this informationcan be used to control storage of the signal, presentation to theviewer, etc.

Such a mechanism may be used to introduce various data items to theprogram logic which are not properly conceived of as television signals.For instance, software updates or other data may be passed to thesystem. The program logic receiving this data from the television streammay impose controls on how the data is handled, such as requiringcertain authentication sequences and/or decrypting the embeddedinformation according to some previously acquired key. Such a methodworks for normal broadcast signals as well, leading to an efficientmeans of providing non-TV control information and data to the programlogic.

Additionally, although a VCR is specifically mentioned above, anymultimedia recording device (e.g., a Digital Video Disk-Random AccessMemory (DVD-RAM) recorder) is easily substituted in its place.

Although the invention is described herein with reference to thepreferred embodiment, other applications may be substituted for thoseset forth herein without departing from the spirit and scope of thepresent invention. For example, the invention can be used in thedetection of gambling casino crime. The input section of the inventionis connected to the casino's video surveillance system. Recorded videois cached and simultaneously output to external VCRs. The user canswitch to any video feed and examine (i.e., rewind, play, slow play,fast forward, etc.) a specific segment of the recorded video while theexternal VCRs are being loaded with the real-time input video. VideoStream Tag Architecture

Referring again to FIG. 12, tags are abstract events which occur in atelevision stream 1201. They may be embedded in the VBI of an analogsignal, or in a private data channel in an MPEG2 multiplex. As describedabove, tags can be embedded in the closed caption (CC) fields andextracted into a circular buffer 1203 or memory allocation schema. Theword parser 1204 identifies unique tags during its scan of the CC data.Tags are interspersed with the standard CC control codes. Tags may alsobe generated implicitly, for instance, based on the current time andprogram being viewed.

The invention provides a mechanism called the TiVo Video Tag Authoring(TVTAG) system for inserting tags (TiVo tags) into a video stream priorto broadcast. With respect to FIGS. 14, 16, and 17, the TVTAG systemconsists of a video output source 1401, a compatible device forinserting Vertical Blanking Interval (VBI) closed-captioning informationand outputting captioned video 1402, a video monitor 1405, and asoftware program for controlling the VBI insertion device to incorporatetag data objects in the form of closed-caption information in the videostream 1406. The tagged video is retransmitted immediately 1404 orstored on a suitable medium 1403 for later transmission.

The TVTAG software 1406, in its most basic implementation, isresponsible for controlling the VBI Insertion device 1402. The TVTAGsoftware 1406 communicates with the VBI insertion device 1402 by meansof standard computer interfaces and device control code protocols. Whenan operator observing the video monitor 1405 determines that the desiredtag insertion point has been reached, he presses a key, causing the TiVotag data object to be generated, transmitted to the VBI insertion device1402, and incorporated in the video stream for transmission 1404 orstorage 1403.

The TVTAG software has the additional capability of controlling thevideo input source 1401 and the video output storage device 1403. Theoperator selects the particular video 1602 and has the ability to pausethe video input stream to facilitate overlaying a graphic element 1702on the monitor, and positioning it by means of a pointing device, suchas a mouse. The positioning of the graphic element 1702 is alsoaccomplished through the operator interface 1601. The operator inputsthe position of the graphic using the X position 1605 and the Y position1604.

The graphic element and positioning information are then incorporated inthe TiVo tag data object (discussed below) and the time-code or frame ofthe video noted. When the operator is satisfied, playback and record areresumed. The tag is then issued through the insertion device with thehighest degree of accuracy.

Referring to FIG. 15, in another embodiment of the TVTAG system, thesoftware program takes the form of a standard Internet protocol Web pagedisplayed to operator(s) 1505. The Web page causes the TiVo tag objectto be generated by a script running on a remote server 1504. The server1504 controls the VBI insertion device 1502, the video source 1501, andrecording devices 1503. The remote operator(s) 1505 can receive from theserver 1504 a low or high-bandwidth version of the video stream for useas a reference for tag insertion. Once the necessary tag data objectinformation has been generated and transmitted, it can bebatch-processed at a later time by the server 1504.

Another embodiment of the invention integrates the software with popularnon-linear video editing systems as a “plug-in”, thereby allowing theTiVo tag data objects to be inserted during the video productionprocess. In this embodiment, the non-linear editing system serves as thesource and storage system controller and also provides graphic placementfacilities, allowing frame-accurate placement of the TiVo tag dataobject.

With respect to FIG. 18, tags are integrated into the video streambefore or at the video source 1801. The video stream is then transmittedvia satellite 1802, cable or other terrestrial transmission method 1803.The receiver 1804 receives the video stream, recognizes the tags andperforms the appropriate actions in response to the tags. The viewersees the resultant video stream via the monitor or television set 1805.

The invention provides an architecture that supports taking variousactions based on tags in the video stream. Some examples of theflexibility that TiVo tags offer are:

-   -   It is desirable to know when a network promotion is being viewed        so that the viewer might be presented with an option to record        the program at some future time. TiVo tags are added into the        promotion that indicate the date, time, and channel when the        program airs. Active promos are described in further detail        below.    -   A common problem is the baseball game overrun problem. VCRs and        Digital Video Recorders (DVR) cut off the end of the baseball        game whenever the game runs over the advertised time slot. A        TiVo tag is sent in the video stream indicating that the        recording needs to continue. A TiVo tag is also sent telling the        system to stop the recording because the game has ended.    -   Boxing matches often end abruptly, causing VCRs and DVRs to        record fill-in programs for the rest of the reserved time        period. A TiVo tag is sent to indicate that the program has        ended, telling the system to stop the recording.    -   Referring to FIG. 19, advertisements are tagged so a locally or        remotely stored advertisement might be shown instead of a        national or out of the area advertisement. Within the video        stream 1901, the program segment 1902 (commercial or other        program segment) to be overlaid is tagged using techniques such        as the TVTAG system described above. The TiVo tags tell the        invention 1905 the start and end points of the old program        segment 1902. A single tag 1903 can be added that tells the        invention 1905 the duration of the old program segment 1902 or a        tag is added at the beginning 1903 and end 1904 of the old        program segment to indicate the start and end of the segment        1902. When the TiVo tag is detected, the invention 1905 finds        the new program segment 1906 and simply plays it back in place        of the old program segment 1902, reverting to the original        program 1901 when playback is completed. The viewer 1907 never        notices the transition.

There are three options at this point:

-   -   1) The system 1905 can continue to cache the original program,        so if the viewer 1907 rewinds the program 1901 and plays it        again, he sees the overlaid segment;    -   2) The old program segment 1902 is replaced in the cache too, so        the viewer never sees the overlaid segment; or    -   3) The system caches the original segment 1902 and reinterprets        the tags on playback. However, without intelligent tag        prefetching, this only works correctly if the viewer backs up        far enough so the system sees the first tag in the overlaid        segment.    -   This problem is solved by adding the length of the old program        segment to the start 1903 and end 1904 tag. Another approach is        to match tags so that the start tag 1903 identifies the end tag        1904 to the system. The system 1905 knows that it should be        looking for another tag when it fast forwards or rewinds over        one of the tags. The pair of tags 1903, 1904 include a unique        identifier. The system 1905 can then search ahead or behind for        the matching tag and replace the old program. There is a limit        to the amount of time or length of frames that the system can        conduct the prefetch. This can be included in the tag or        standardized. Including the limit in the tag is the most        flexible approach.

The program segment to be played back is selected based, for example, onlocale, the time of day, program material, or on the preference engine(described in application Ser. No. 09/422,121 owned by the Applicant).Using the preference engine, the appropriate program segment from localor server storage 1906 is selected according to the viewer's profile.The profile contains the viewer's viewing habits, program preferences,and other personal information. The stored program segments 1906 haveprogram objects describing their features as well, which are searchedfor best match versus the preference vector.

Clearly, there must be a rotation mechanism among commercials to avoidad burnout. The preference vector can be further biased by generating anerror vector versus the program data for the currently viewed program,and using this error vector to bias the match against the commercialinventory on disk 1906. For example, if the viewer is watching a soapopera and the viewer's preference vector is oriented towards sportsshows, then the invention will select the beer commercial in favor ofthe diaper commercial.

A tag can also be used to make conditional choices. The tag contains apreference weighting of its own. In this case, the preference weightingis compared to the preference vector and a high correlation causes theinvention to leave the commercial alone. A low correlation invokes themethod above.

NOTE: In all of these cases the system 1905 has more than enough time tomake a decision. The structure of the pipeline routinely buffers ½second of video, giving lots of time between input and output to changethe stream. If more time is needed, add buffering to the pipeline. Ifplaying back off disk, then the system creates the same time delay byreading ahead in the stream.

Also note that commercials can also be detected using the methoddescribed in application Ser. No. 09/187,967 entitled “Analog VideoTagging and Encoding System,” also owned by the Applicant. The same typeof substitution described above can be used when tags described in theaforementioned application are used.

With respect to FIGS. 19 and 22, tags allow the incorporation ofcommercial “zapping.” Since tags can be used to mark the beginning 1903and ending 1904 points of a commercial, they can be skipped as well aspreempted. The viewer simply presses the jump button 2205 on the remotecontrol 2201. The system searches for the end tag and resumes playbackat the frame following the frame associated with the tag. The number ofcommercials skipped is dependent upon the amount of video streambuffered.

Depending on the viewer's preset preferences, the system 1905 itself canskip commercials on live or prerecorded programs stored in memory 1906.Skipping commercials on live video just requires a larger amount ofbuffering in the pipeline as described above. Allowing the system toskip commercials on recorded programs presents the viewer with acontinuous showing of the program without any commercial interruptions.

Tags are added to program material to act as indexes. The viewer, forexample, can jump to each index within the program by pressing the jumpbutton 2205 on the remote control 2201.

Tags are also used for system functions. As noted above, the systemlocally stores program material for its own use. The system 1905 mustsomehow receive the program material. This is done by tuning in to aparticular channel at off hours. The system 1905 searches for the tag inthe stream 1901 that tells it to start recording. The recording iscomprised of a number of program segments delimited by tags 1903, 1904that identify the content and possibly a preference vector. A tag at theend of the stream tells the system 1905 to stop recording. The programsegments are stored locally 1906 and indexed for later use as describedabove.

The invention incorporates the following design points:

-   -   The design provides for a clear separation of mechanism and        policy.    -   Internally, tags are viewed as abstract events which trigger        policy modules. Mapping of received tag information to these        internal abstractions is the responsibility of the source        pipeline object.    -   Abstract tags are stored in the PesBuf stream as if they were        just another segment. This allows the handling of arbitrary        sized tags with precise timing information. It also allows tags        to persist as part of recorded programs, so that proper actions        are taken no matter when the program is viewed.    -   Tags may update information about the current program, future        programs, etc. This information is preserved for recorded        programs.    -   Tags can be logged as they pass through the system. It also        possible to upload this information. It may not be necessary to        preserve all information associated with a tag.    -   Tags can be generated based on separate timelines. For example,        using a network station log to generate tags based on time and        network being viewed. Time-based tags are preserved in recorded        streams.        Time-Based Tags

Referring to FIG. 20, time-based tags are handled by a Time-based TagRecognizer 2012. This object 2012 listens for channel change events and,when a known network is switched to, attempts to retrieve a “time log”for that network. If one is present, the object 2012 builds a tagschedule based on the current time. As the time occurs for each tag, theobject 2012 sends an event to the source object 2001 indicating the tagto be inserted. The source object 2001 inserts the tag into the nextavailable position in the current PesBuf under construction. The next“available” position may be determined based on frame boundaries orother conditions.

The Role of the Source Object

The source object 2001 is responsible for inserting tags into the PesBufstream it produces. This is assuming there are separate source objectsfor analog input and digital TV sources.

There are a number of different ways that tags may appear in an analogstream:

-   -   Within the EDS field.    -   Implicitly using the CC field.    -   Modulated onto the VBI, perhaps using the ATVEF specification.    -   Time Based

In a digital TV stream, or after conversion to MPEG from analog:

-   -   In-band, using TiVo Tagging Technology.    -   MPEG2 Private data channel.    -   MPEG2 stream features (frame boundaries, etc.).    -   Time-based tags.

The source object 2001 is not responsible for parsing the tags andtaking any actions. Instead, the source object 2001 should solely beresponsible for recognizing potential tags in the stream and adding themto the PesBuf stream.

Tag Recognition and Action

Conceptually, all tags may be broken up into two broad groups: thosethat require action upon reception, such as recording a program; andthose that require action upon presentation, i.e., when the program isviewed.

Reception Tag Handling

Tags that require action upon reception are handled as follows: a newReception Tag Mechanism subclass 2003 of the TmkPushSwitch class 2002 iscreated. As input streams pass through this class 2003 between thesource object 2001 and the program cache transform 2013, the class 2003recognizes reception tags and takes appropriate actions.

Reception tags are generally handled once and then disabled.

Presentation Tag Handling

Tags that require actions upon presentation are handled as follows: anew Presentation Tag Mechanism subclass 2007 of the TmkPullSwitch class2008 is created. As output streams pass through this class 2007 betweenthe program cache transform 2013 and the sink object 2011, the class2007 recognizes presentation tags and takes appropriate actions.

Tag Policy Handling

Tag reception handling is only permitted if there is aTagReceptionPolicy object 2009 present for the current channel. Tagpresentation handling is only permitted if there is aTagPresentationPolicy object 2010 for the source channel.

The TagPolicy objects describe which tags are to be recognized, and whatactions are allowed.

When an input channel change occurs, the reception tag object isnotified, and it fetches the TagReceptionPolicy object 2009 (if any) forthat channel, and obeys the defined policy.

When an output channel change occurs, the presentation tag object isnotified, and it fetches the TagPresentationPolicy object 2010 (if any)for that channel, and obeys the defined policy.

Tag Logging

The reception of tags may be logged into the database. This only occursif a TagReceptionPolicy object 2009 is present, and the tag loggingattribute is set. As an example, the logging attribute might be set, butno reception actions allowed to be performed. This allows passivelogging of activity in the input stream.

Pipeline Processing Changes

It is important to support updates of information about the currentshowing. The following strategy is proposed:

-   -   Whenever the input source is changed or a new showing starts, a        copy is made of the showing object, and all further operations        in the pipeline work off this copy.    -   Update tags are reception tags; if permitted by policy, the        copied showing object is updated.    -   If the current showing is to be recorded, the copy of the        showing object is saved with it, so that the saved program has        the proper information saved with it.    -   The original showing object is not modified by this process.    -   The recorder must be cognizant of changes to the showing object,        so that it doesn't, for instance, cut off the baseball game        early.        Tag Interpretation vs. Tag State Machine

Tags are extremely flexible in that, once the TagPolicy object has beenused to identify a valid tag, standardized abstract tags are interpretedby the Tag Interpreter 2005 and operational tags are executed by theTiVo Tag State Machine 2006. Interpreted tags trigger a predefined setof actions. Each set of actions have been preprogrammed into the system.

State machine tags are operational tags that do not carry executablecode, but perform program steps. This allows the tag originator tocombine these tags to perform customized actions on the TiVo system.State machine tags can be used to achieve the same results as aninterpreted tag, but have the flexibility to dynamically change the setof actions performed.

Abstract Interpreted Tags

The set of available abstract tags is defined in a table called theTag/Action table. This table is typically stored in a database object.There are a small number of abstract actions defined. These actions fallinto three general categories:

-   -   Viewer visible actions (may include interaction).    -   Meta-information about the stream (channel, time, duration,        etc.).    -   TiVo control tags.

Tags which cause a change to the on-disk database, or cause implicitrecording, must be validated. This is accomplished through control tags.

Viewer Visible Tags

—Menu

This tag indicates that the viewer is to be presented with a choice. Thedata associated with the tag indicates what the choice is, and otherinteresting data, such as presentation style. A menu has an associatedinactivity timeout.

The idea of the menu tag is that the viewer is offered a choice. If theviewer isn't present, or is uninterested, the menu should disappearquickly. The menu policy may or may not be to pause the current program.The presentation of the menu does not have to be a list.

—Push Alternate Program Conditional

This tag indicates that some alternate program should be played if somecondition is true. The condition is analyzed by the policy module. Itmay always be true.

—Pop Alternate Program Conditional

This tag reverts to the previous program. If a program ends, then thealternate program stack is popped automatically. All alternate programsare popped if the channel is changed or the viewer enters the TiVoCentral menu area.

Alternate programs are a way of inserting arbitrary sequences into theviewed stream. The conditional data is not evaluated at the top level.Instead, the policy module must examine this data to make choices. This,for example, can be used to create “telescoping” ads.

—Show Indicator Conditional

This tag causes an indication to be drawn on the screen. Indicators arenamed, and the set of active indicators may be queried at any time. Thetag or tag policy may indicate a timeout value at which time theindicator is derived.

—Clear Indicator Conditional

This tag causes an active indication to be removed. All indicators arecleared if the channel is changed or the viewer enters the TiVo Centralmenu area.

Indicators are another way to offer a choice to the viewer withoutinterrupting program flow. They may also be used to indicate conditionsin the stream that may be of interest. For example, “Active Promo” iscreated by providing a program object ID as part of the tag data,allowing that program to be selected. If the viewer hits a particularkey while the indicator is up, then the program is scheduled forrecording.

Meta-Information Tags

—Current Showing Information

This tag is a general bucket for information about the current showing.Each tag typically communicates one piece of information, such as thestart time, end time, duration, etc. This tag can be used to “lengthen”a recording of an event.

—Future Showing Information

This tag is similar to the above, but contains information about afuture showing. There are two circumstances of interest:

-   -   The information refers to some showing already resident in the        database. The database object is updated as appropriate.    -   The information refers to a non-existent showing. A new showing        object is created and initialized from the tag.        TiVo Control Tags        —Authorize Modification

This tag is generally encrypted with the current month's security key.The lifetime of the authorization is set by policy, probably to an houror two. Thus, the tag needs to be continually rebroadcast ifmodifications to local TiVo system states are permitted.

The idea of this tag is to avoid malicious (or accidental) attacks usinginherently insecure tag mechanisms such as EDS. If a network providesEDS information, we first want to ensure that their tags are accurateand that attacks on the tag delivery system are unlikely. Then, we wouldwork with that network to provide an authorization system thatcarouseled authorization tags on just that network. Unauthorized tagsshould never be inserted into the PES stream by the source object.

—Record Current Conditional

This tag causes the current program to be saved to disk starting fromthis point. The recording will cease when the current program ends.

—Stop Recording Current Conditional

This tag ceases recording of the current program.

—Record Future Conditional

A showing object ID is provided (perhaps just sent down in a FutureShowing tag). The program is scheduled for recording at a backgroundpriority lower than explicit viewer selections.

—Cancel Record Future Conditional

A showing object ID is provided. If a recording was scheduled by aprevious tag for that object, then the recording is canceled.

These tags, and the Future Showing tag, may be inserted in an encrypted,secure format. The source object will only insert these tags in the PESstream if they are properly validated.

One of the purposes of these tags is to automatically trigger recordingof TiVo inventory, such as loopsets, advertisements, interstitials, etc.A later download would cause this inventory to be “installed” andavailable.

—Save File Conditional

This tag is used to pass data through the stream to be stored to disk.For instance, broadcast Web pages would be passed through thismechanism.

—Save Object Conditional

This tag is used to pass an object through the stream to be stored todisk. Storing the object follows standard object updating rules.

The following is an example of an implementation using presentation tagsinserted into the Closed Captioning (CC) part of a stream. The CC partof the stream was chosen because it is preserved when a signal istransmitted and digitized and decoded before it reaches the user'sreceiver. There are no guarantees on the rest of the VBI signal. Many ofthe satellite systems strip out everything except the closed captioningwhen encoding into MPEG-2.

There is a severe bandwidth limitation on the CC stream. The data ratefor the CC stream is two 7-bit bytes every video frame. Furthermore, toavoid collision with the control codes, the data must start at 0×20,thus effectively limiting it to about 6.5-bit bytes (truncate to 6-bitbytes for simplicity). Therefore, the bandwidth is roughly 360bits/second. This rate gets further reduced if the channel is sharedwith real CC data. In addition, extra control codes need to be sent downto prevent CC-enabled televisions from attempting to display the TiVotags as CC text.

Basic Tag Layout

This section describes how the tags are laid out in the closedcaptioning stream. It assumes a general familiarity with the closedcaptioning specification, though this is not crucial.

Making Tags Invisible

A TiVo Tag placed in a stream should not affect the display on a closedcaptioning enabled television. This is achieved by first sending down a“resume caption loading” command (twice for fault tolerance), followedby a string of characters that describes the tag followed by an “erasenondisplayed memory” command (twice for fault tolerance). What this doesis to load text into offscreen memory, and then clear the memory. Aregular TV with closed captioning enabled will not display this text (asper EIA-701 standard).

This works as long as the closed captioning decoder is not in “roll-up”or “scrolling” mode. In this mode, a “resume caption loading” commandwould cause the text to be erased. To solve this problem, TiVo Tags willbe accepted and recognized even if they are sent to the second closedcaptioning channel. This way, even if closed captioning channel 1 is setup with scrolling text, we can still send the tag through closedcaptioning channel 2.

Tag Encoding

The text sent with a TiVo Tag consists of the letters “Tt”, followed bya single character indicating the length of the tag, followed by the tagcontents, followed by a CRC for the tag contents. The letters “Tt” aresufficiently unique that it is unlikely to encounter these in normal CCdata. Furthermore, normal CC data always starts with a position controlcode to indicate where on the screen the text is displayed. Since we arenot displaying onscreen, there is no need for this positioning data.Therefore, the likelihood of encountering a “Tt” immediately after a“resume caption loading” control code is sufficiently rare that we canalmost guarantee that this combination is a TiVo tag (though theimplementation still will not count on this to be true).

The single character indicating the length of the tag is computed byadding the tag length to 0×20. If the length is 3 characters, forexample, then the length character used is 0×23 (‘#’). So as not tolimit the implementation to a length of 95 (since there are only 96characters in the character set), the maximum length is defined as 63.If longer tags are needed, then an interpretation for the other 32possible values for the length character can be added.

The possible values for the tag itself are defined in the Tag Typessection below.

The CRC is the 16 bit CRC-CCITT (i.e., polynomial=x{circumflex over( )}16+x{circumflex over ( )}12+x{circumflex over ( )}5+1). It is placedin the stream as three separate characters. The first character iscomputed by adding 0×20 to the most significant six bits of the CRC. Thenext character is computed by adding 0×20 to the next six bits of theCRC. The last character is computed by adding 0×20 to the last four bitsof the CRC.

Tag Types

This section details an example of a TiVo Tag. Note that every tagsequence begins with at least one byte indicating the tag type.

iPreview Tag

With respect to FIG. 17, an iPreview tag contains four pieces ofinformation. The first is the 32 bit program ID of the program beingpreviewed. The second contains how much longer the promotion is going tolast. The third piece is where on the screen 1701 to place an iPreviewalert 1702 and the last piece is what size iPreview alert to use.

The screen location for the iPreview alert is a fraction of the screenresolution in width and height. The X coordinate uses 9 bits to dividethe width, so the final coordinate is given as:X=(x_resolution/511)*xval. If the xval is given as 10, on a 720×486screen (using CCIR656 resolution), the X coordinate would be 14. The Ycoordinate uses 8 bits to divide the height, so the final coordinate isgiven as: Y=(y_resolution/255)*yval. The X,Y coordinates indicate thelocation of the upper-left corner of the bug graphic.

If the value of X and Y are set to the maximum possible values (i.e.,x=511, y=255), then this indicates that the author is giving the systemthe job of determining its position. The system will place the bug at apredetermined default position. The rationale for using the max valuesto indicate the default position is that it is never expected that a“real” position will be set to these values since that would put theentire bug graphic offscreen.

The size field is a four bit number that indicates what size any alertgraphic should be. The 16 possible values of this field correspond topredefined graphic sizes that the settop boxes should be prepared toprovide.

The timeout is a ten bit number indicating the number of frames left inthe promotion. This puts a 34 second lifetime limit on this tag. If apromotion is longer, then the tag needs to be repeated. Note that thetimeout was “artificially limited” to 10 bits to limit exposure toerrors. This is to limit the effect it will have on subsequentcommercials if an author puts a malformed timeout in the tag.

The version is a versioning number used to identify the promo itself.Instead of bit-packing this number (and thus limiting it to 6 bits), thefull closed captioning character set is used, which results in 96possibilities instead of 64 (2{circumflex over ( )}6). The versionnumber thus needs to be within the range 0-95.

The reserved character is currently unused. This character needs toexist so that the control codes end up properly aligned on the 2-byteboundaries.

The first character of an iPreview tag is always “i”.

All of the data fields are packed together on a bit boundary, and thenbroken into six bit values which are converted into characters (byadding 0×20) and transmitted. The order of the fields are as follows:

-   -   32 bits: program ID    -   9 bits: X location    -   8 bits: Y location    -   4 bits: graphic size    -   10 bits: timeout    -   1 character: version    -   1 character: reserved

The data fields total 66 bits which requires 11 characters to send +1character for version and 1 character for reserved. The exact contentsof each character are:

-   -   1) 0×20+ID[31:26]    -   2) 0×20+ID[25:20]    -   3) 0×20+ID[19:14]    -   4) 0×20+ID[13:8]    -   5) 0×20+ID[7:2]    -   6) 0×20+ID[1:0]X[8:5]    -   7) 0×20+X[4:0]Y[7]    -   8) 0×20+Y[6:1]    -   9) 0×20+Y[0]size[3:0]    -   10) 0×20+Y[0]size[3:0]timeout[9]    -   11) 0×20+timeout[8:3]    -   12) 0×20+timeout[2:0]    -   13) 0×20+version    -   14) reserved

Including the first character “i”, the length of the iPreview tag is 14characters+3 CRC characters. With the tag header (3 characters), thismakes a total length of 20 characters which can be sent down over 10frames. Adding another 4 frames for sending “resume caption loading”twice and “erase nondisplayed memory” twice means an iPreview tag willtake 14 frames (0.47 seconds) to broadcast.

A complete iPreview tag consists of:

-   -   Resume caption loading Resume caption loading T t 1        (0×20+17=0×31=0110001=“1”) i<13 character iPreview tag>3        character CRC Erase nondisplayed memory Erase nondisplayed        memory        Parity Debugging Character

Currently, the parity bit is being used as a parity bit. However, sincea CRC is already included, there is no need for the error-checkingcapabilities of the parity bit. Taking this a step further, the paritybit can be used in a clever way. Since a closed captioning receivershould ignore any characters with an incorrect parity bit, a better useof the limited bandwidth CC channel can be had by intentionally usingthe wrong parity. This allows the elimination of the resume captionloading and erase nondisplayed memory characters, as well as making iteasier to “intersperse” TiVo tags among existing CC data.

iPreview Viewer Interaction

Referring to FIGS. 17, 20, 21 and 22, the iPreview tag causes the TagInterpreter 2005 to display the iPreview alert 1702 on the screen 1701.The iPreview alert 1702 tells the viewer that an active promo isavailable and the viewer can tell the TiVo system to record the futureshowing. The viewer reacts to the iPreview alert 1702 by pressing theselect button 2204 on the remote control 2201.

The Tag Interpreter 2005 waits for the user input. Depending on theviewer's preset preferences, the press of the select button 2204 resultsin the program automatically scheduled by the Tag Interpreter 2005 forrecording, resulting in a one-touch record, or the viewer is presentedwith a record options screen 2101. The viewer highlights the record menuitem 2102 and presses the select button 2204 to have the programscheduled for recording.

The tag itself has been interpreted by the Tag Interpreter 2005. The TagInterpreter 2005 waits for any viewer input through the remote control2201. Once the viewer presses the select button 2204, the TagInterpreter 2005 tells the TiVo system to schedule a recording of theprogram described by the 32 bit program ID in the iPreview tag.

With respect to FIGS. 20, 22, and 23, the iPreview tag is also used forother purposes. Each use is dictated by the context of the programmaterial and the screen icon displayed. Obviously the system cannotinterpret the program material, but the icon combined with the programID tell the Tag Interpreter 2005 what action to take. Two examples arethe generation of a lead and a sale.

The process of generating a lead occurs when, for example, a car ad isbeing played. An iPreview icon appears 2301 on the screen and the viewerknows that he can press the select button 2204 to enter an interactivemenu.

A menu screen 2302 is displayed by the Tag Interpreter 2005 giving theuser the choice to get more information 2303 or see a video of the car2304. The viewer can always exit by pressing the live TV button 2202. Ifthe viewer selects get more information 2303 with the up and down arrowbutton 2203 select button 2204, then the viewer's information is sent tothe manufacturer 2305 by the Tag Interpreter 2005, thereby generating alead. The viewer returns to the program by pressing the select button2204.

Generating a sale occurs when a product, e.g., a music album ad, isadvertised. The iPreview icon 2301 appears on the screen. The viewerpresses the select button 2204 and a menu screen 2307 is displayed bythe Tag Interpreter 2005.

The menu screen 2307 gives the viewer the choice to buy the product 2308or to exit 2309. If the viewer selects yes 2308 to buy the product, thenthe Tag Interpreter 2005 sends the order to the manufacturer with theviewer's purchase information 2310. If this were a music album ad, theviewer may also be presented with a selection to view a music video bythe artist.

Whenever the system returns the viewer back to the program, it returnsto the exact point that the viewer had originally exited from. Thisgives the viewer a sense of continuity.

The concept of redirection is easily expanded to the Internet. TheiPreview icon will appear as described above. When the viewer pressesthe select button 2204 on the remote control 2201, a Web page is thendisplayed to the viewer. The viewer then interacts with the Web page andwhen done, the system returns the viewer back to the program that he waswatching at the exact point from which the viewer had exited.

Using the preference engine as noted above, the information shown to theviewer during a lead or sale generation is easily geared toward thespecific viewer. The viewer's viewing habits, program preferences, andpersonal information are used to select the menus, choices, and screenspresented to the viewer. Each menu, choice and screen has an associatedprogram object that is compared to the viewer's preference vector.

For example, if a viewer is male and the promo is for Chevrolet, thenwhen the viewer presses the select button, a still of a truck isdisplayed. If the viewer were female, then a still of a convertiblewould be displayed.

Note that the Tag State Machine 2006 described below is fully capable ofperforming the same steps as the Tag Interpreter 2005 in the aboveexamples.

The TiVo Tag State Machine

Referring again to FIG. 20, a preferred embodiment of the inventionprovides a Tag State Machine (TSM) 2006 which is a mechanism forprocessing abstract TiVo tags that may result in viewer-visible actionsby the TiVo Receiver.

A simple example is the creation of an active promo. As demonstratedabove, an active promo is where a promotion for an upcoming show isbroadcast and the viewer is immediately given the option of having theTiVo system record that program when it actually is broadcast.

Hidden complexities underlie this simple example: some indicator must begenerated to alert the viewer to the opportunity; the indicator must bebrought into view or removed with precision; accurate identification ofthe program in question must be provided; and the program within whichthe active promo appears may be viewed at a very different time thenwhen it was broadcast.

Creation and management of the TiVo tags is also challenging. It isimportant to cause as little change as possible to existing broadcastpractices and techniques. This means keeping the mechanism as simple aspossible for both ease of integration into the broadcast stream and forrobust and reliable operation.

Principles of Tags

As previously noted, it is assumed that the bandwidth available forsending tags is constrained. For example, the VBI has limited spaceavailable which is under heavy competition. Even in digital televisionsignals, the amount of out-of-band data sent will be small since mostconsumers of the signal will be mainly focused on television programmingoptions.

A tag is then a simple object of only a few bytes in size. More complexactions are built by sending multiple tags in sequence.

The nature of broadcast delivery implies that tags will get lost due tosignal problems, sunspots, etc. The TSM incorporates a mechanism forhandling lost tags, and insuring that no unexpected actions are takendue to lost tags.

In general, viewer-visible tag actions are relevant only to the channelon which they are received; it is assumed that tag state is discardedafter a channel change.

Physical tags are translated into abstract tags by the source object1901 receiving the physical tag. Tags are not “active agents” in thatthey carry no executable code; functioning the TSM may result inviewer-visible artifacts and changes, but the basic operation of theTiVo receiver system will remain unaffected by the sequence of tags. Iftags could contain executable code, such as the Java byte streamscontemplated by the ATVEF, the integrity of the TiVo viewing experiencemight be compromised by poorly written or malicious software.

All tag actions are governed by a matching policy object matched to thecurrent channel. Any or all actions may be enabled or disabled by thisobject; the absence of a policy object suppresses all tag actions.

The Basic Abstract Tag

All abstract tags have a common infrastructure. The following componentsare present in any abstract tag:

—Tag Type (1 byte)

The type 0 is disallowed. The type 255 indicates an “extension” tag,should more than 254 tag values be required at some future time.

—Tag Sequence (1 byte)

This unsigned field is incremented for each tag that is part of asequence. Tags which are not part of a sequence must have this field setto zero. A tag sequence of one indicates the start of a new sequence; asequence may be any length conceptually, but it will be composed ofsegments of no more than 255 tags in order.

Each tag type has an implicit sequence length (which may be zero); thesequence number is introduced to handle dropouts or other forms of tagloss in the stream. In general, if a sequence error occurs, the entiretag sequence is discarded and the state machine reset.

Tags should be checksummed in the physical domain. If the checksumdoesn't match, the tag is discarded by the source object. This willresult in a sequence error and reset of the state machine.

—Tag Timestamp (8 bytes)

This is the synchronous time within the TV stream at which the tag wasrecognized. This time is synchronous to all other presentation timesgenerated by the TiVo Receiver. This component is never sent, but isgenerated by the receiver itself.

—Tag Data Length (2 bytes)

This is the length of any data associated with the tag. Theinterpretation of this data is based on the tag type. The physicaldomain translator should perform some minimal error checking on thedata.

The Tag State Machine

The TSM is part of the Tag Presentation Mechanism, which is in-line withvideo playback.

Conceptually, the TSM manages an abstract stack of integer values withat least 32 bits of precision, or sufficient size to hold an object ID.The object ID is abstract, and may or may not indicate a real object onthe TiVo Receiver—it may otherwise need to be mapped to the correctobject. The stack is limited in size to 255 entries to limitdenial-of-service attacks.

The TSM also manages a pool of variables. Variables are named with a2-byte integer. The variable name 0 is reserved. “User” variables may bemanipulated by tag sequences; such variables lie between 1 and2{circumflex over ( )}15-1. “System” variables are maintained by theTSM, and contain values about the current TiVo Receiver, such as: thecurrent program object ID; the TSM revision; and other usefulinformation. These variables have names between 2{circumflex over ( )}15and 2{circumflex over ( )}16-1. The number of user variables may belimited within a TSM; a TSM variable indicates what this limit is.

The tag data is a sequence of TSM commands. Execution of these commandsbegins when the tag is recognized and allowed. TSM commands are byteoriented and certain commands may have additional bytes to support theirfunction.

The available TSM commands may be broken down into several classes:

Data Movement Commands

-   -   push_byte—push the byte following the command onto the stack.    -   push_short—push the short following the command onto the stack.    -   push_word—push the word following the command onto the stack.        Variable Access Commands    -   push_var—push the variable named in the 16-bit quantity        following the command.    -   pop_var—pop into the variable named in the 16-bit quantity        following the command.    -   copy_var—copy into the variable named in the 16-bit quantity        following the command from the stack.        Stack Manipulation Commands    -   swap—swap the top two stack values.    -   pop—toss the top stack value.        Arithmetic Commands    -   add_byte—add the signed byte following the command to the top of        stack.    -   add_short—add the signed short following the command to the top        of stack.    -   add_word—add the signed word following the command to the top of        stack.    -   and—and the top and next stack entries together, pop the stack        and push the new value.    -   or—or the top and next stack entries together, pop the stack and        push the new value.        Conditional Commands        (Unsigned Comparisons Only)    -   brif_zero—branch to the signed 16-bit offset following the        command if the top of stack is zero.    -   brif_nz—branch to the signed 16-bit offset following the command        if the top of stack is not zero.    -   brif_gt—branch to the signed 16-bit offset following the command        if the top of stack is greater than the next stack entry.    -   brif_ge—branch to the signed 16-bit offset following the command        if the top of stack is greater than or equal to the next stack        entry.    -   brif_le—branch to the signed 16-bit offset following the command        if the top of stack is less than or equal to the next stack        entry.    -   brif_lt—branch to the signed 16-bit offset following the command        if the top of stack is less than the next stack entry.    -   brif_set—branch to the signed 16-bit offset following the        command if there are bits set when the top and next stack        entries are ANDed together.        Action Commands    -   exec—execute tag action on the object ID named on top of stack.    -   fin—terminate tag taking no action.        System Variables    -   32768 (TAG)—value of current tag.        Times in GMT:    -   32769 (YEAR)—current year (since 0).    -   32770 (MONTH)—current month (1-12).    -   32771 (DAY)—day of month (1-31).    -   32772 (WDAY)—day of week (1-7, starts Sunday).    -   32773 (HOUR)—hour of the day (0-23).    -   32774 (MIN)—minute of the hour (0-59).    -   32775 (SEC)—seconds of the minute (0-59).        TiVo Receiver State:    -   32800 (SWREL)—software release (in x.x.x notation in bytes).    -   32801 (NTWRK)—object ID of currently tuned network.    -   32802 (PRGRM)—object ID of currently tuned program.    -   32803 (PSTATE)—current state of output pipeline:        -   0—normal playback        -   1—paused        -   2—slo-mo        -   10—rewind speed 1        -   11—rewind speed 2        -   . . .        -   20—ff speed 1        -   21—ff speed 2        -   . . .            Tag Execution State:    -   32900 (IND)—indicator number to display or take down.    -   32901 (PDURING)—state of the pipeline while tag is executing.    -   32902 (ALTP)—alternate program object ID to push on play stack.    -   32903 (SELOBJ)—program object ID to record if indicator        selected.    -   33000 (MENU1)—string object number for menu item 1.    -   33001 (MENU2)—string object number for menu item 2.    -   33009 (MENU10)—string object number for menu item 9.    -   33100 (PICT1)—picture object number for menu item 1.    -   33101 (PICT2)—picture object number for menu item 2.    -   33109 (PICT10)—picture object number for menu item 10.    -   33200 (MSELOBJ1)—program object ID to record if menu item        selected.    -   33201 (MSELOBJ2)—program object ID to record if menu item        selected.    -   33209 (MSELOBJ10)—program object ID to record if menu item        selected.        Tags    -   Push Alternate Program    -   Pop Alternate Program (auto-pop at end of program)    -   Raise Indicator    -   Lower Indicator    -   Menu        Tag Execution Policy

Execution policy is determined by the TSM. Some suggestions are:

—Menus

Menus are laid out as per standard TiVo menu guidelines. In general,menus appear over live video. Selection of an item typically invokes therecord dialog. It may be best to pause the pipeline during the menuoperation.

—Indicators

With respect to FIGS. 17 and 22, indicators 1702 are lined up at thebottom of the display as small icons. During the normal viewing state,the up arrow and down arrow keys 2203 on the remote control 2201 donothing. For indicators, up arrow 2203 circles through the indicators tothe left, down arrow to the right. The selected indicator has a smallsquare drawn around it. Pushing select 2204 initiates the action. Newindicators are by default selected; if an indicator is removed, thepreviously selected indicator is highlighted, if any.

—Alternate Programs

Alternate programs should appear as part of the video stream, and havefull ff/rew controls. The skip to live button 2202 pops the alternateprogram stack to empty first.

Although the closed caption stream is specifically mentioned above,other transport methods can be used such as the EDS fields, VBI, MPEG2private data channel, etc.

Although the invention is described herein with reference to thepreferred embodiment, one skilled in the art will readily appreciatethat other applications may be substituted for those set forth hereinwithout departing from the spirit and scope of the present invention.Accordingly, the invention should only be limited by the Claims includedbelow.

1. A method for automatic replacement of program segments in amultimedia television broadcast stream at a receiver, comprising:receiving the multimedia television broadcast stream; detecting startand end points of a first program segment in the broadcast stream; andsubstituting the first program segment with a new program segment from aplurality of new program segments during playback of the broadcaststream to a viewer.
 2. The method of claim 1, wherein the detecting stepsearches for tags inserted into the broadcast stream denoting start andend points of program segments.
 3. The method of claim 2, wherein thetags are located in the closed caption area of the broadcast stream. 4.The method of claim 1, wherein the new program segments are stored on astorage device on the receiver.
 5. The method of claim 4, wherein thestorage device is a hard disk.
 6. The method of claim 4, furthercomprising: receiving new program segments via the broadcast stream; andstoring the new program segments on the storage device.
 7. The method ofclaim 1, wherein the new program segments are stored at a remotelyaccessible location.
 8. The method of claim 1, wherein the new programsegment to be played back is selected based on criteria that includesany of: locale, the time of day, program material, the viewer's viewinghabits, the viewer's program preferences, or the viewer's personalinformation.
 9. The method of claim 8, wherein the criteria may resultin the first program segment not being substituted.
 10. The method ofclaim 8, wherein the new program segments have program objectsdescribing their features which are used to select a best matching newprogram segment.
 11. The method of claim 1, wherein a rotation mechanismis used when selecting the new program segments to avoid ad burnout. 12.An apparatus for automatic replacement of program segments in amultimedia television broadcast stream at a receiver, comprising: areceiving module, wherein the receiving module receives the multimediatelevision broadcast stream; a detection module, wherein the detectionmodule detects the start and end points of a first program segment inthe broadcast stream; and a substitution module, wherein thesubstitution module substitutes the first program segment with a newprogram segment from a plurality of new program segments during playbackof the broadcast stream to a viewer.
 13. The apparatus of claim 12,wherein the detection module searches for tags inserted into thebroadcast stream denoting the start and end points of program segments.14. The apparatus of claim 13, wherein the tags are located in theclosed caption area of the broadcast stream.
 15. The apparatus of claim12, wherein the new program segments are stored on a storage device onthe receiver.
 16. The apparatus of claim 15, wherein the storage deviceis a hard disk.
 17. The apparatus of claim 15, further comprising: aprogram segment receiving module, wherein the program segment receivingmodule receives new program segments via the broadcast stream; and astorage module, wherein the storage module stores the new programsegments on the storage device.
 18. The apparatus of claim 12, whereinthe new program segments are stored at a remotely accessible location.19. The apparatus of claim 12, wherein the new program segment to beplayed back is selected based on criteria that includes any of: locale,the time of day, program material, the viewer's viewing habits, theviewer's program preferences, or the viewer's personal information. 20.The apparatus of claim 19, wherein the criteria may result in the firstprogram segment not being substituted.
 21. The apparatus of claim 19,wherein the new program segments have program objects describing theirfeatures which are used to select a best matching new program segment.22. The apparatus of claim 12, wherein a rotation mechanism is used whenselecting the new program segments to avoid ad burnout.
 23. A programstorage medium readable by a computer, tangibly embodying a program ofinstructions executable by the computer to perform method steps forautomatic replacement of program segments in a multimedia televisionbroadcast stream at a receiver, comprising: receiving the multimediatelevision broadcast stream; detecting the start and end points of afirst program segment in the broadcast stream; and substituting thefirst program segment with a new program segment from a plurality of newprogram segments during playback of the broadcast stream to a viewer.24. The method of claim 23, wherein the detecting step searches for tagsinserted into the broadcast stream denoting start and end points ofprogram segments.
 25. The method of claim 24, wherein the tags arelocated in the closed caption area of the broadcast stream.
 26. Themethod of claim 23, wherein the new program segments are stored on astorage device on the receiver.
 27. The method of claim 26, wherein thestorage device is a hard disk.
 28. The method of claim 26, furthercomprising: receiving new program segments via the broadcast stream; andstoring the new program segments on the storage device.
 29. The methodof claim 23, wherein the new program segments are stored at a remotelyaccessible location.
 30. The method of claim 23, wherein the new programsegment to be played back is selected based on criteria that includesany of: locale, the time of day, program material, the viewer's viewinghabits, the viewer's program preferences, or the viewer's personalinformation.
 31. The method of claim 30, wherein the criteria may resultin the first program segment not being substituted.
 32. The method ofclaim 30, wherein the new program segments have program objectsdescribing their features which are used to select a best matching newprogram segment.
 33. The method of claim 23, wherein a rotationmechanism is used when selecting the new program segments to avoid adburnout.